1. ESA Frascati 31 Oct 2014dinter@iup.physik.uni-bremen.de 1 Determination of the light availability in ocean water utilizing Vibrational Raman Scattering Tilman Dinter V. Rozanov, J.P. Burrows, Astrid Bracher ESA Frascati 31 st Oct 2014 Phytooptics Group Dinter et al. submitted

2. ESA Frascati 31 Oct 2014dinter@iup.physik.uni-bremen.de 2 Light availability  Sunlight is the main driver of biological and physical processes in ocean water.  Quantify processes of photosynthesis, biomass and primary production.  For calculations of heat transfer and fluxes.  → climate modeling

3. ESA Frascati 31 Oct 2014dinter@iup.physik.uni-bremen.de 3 Definition of light availability or Depth Integrated Scalar Irradiance (DISI) Radiation energy density: Actinic flux or scalar irradiance:

4. ESA Frascati 31 Oct 2014dinter@iup.physik.uni-bremen.de 4  Defined as number of photons in the water column.  Directly correlated to strength of Vibrational Raman Scattering (VRS).  Depends on solar zenith angle (sza), surface, atmosphere and the absorption and scattering of water body. Definition of light availability or Depth Integrated Scalar Irradiance (DISI)

5. ESA Frascati 31 Oct 2014dinter@iup.physik.uni-bremen.de 5 Vibrational Raman Scattering in liquid water What is Vibrational RAMAN Scattering in liquid water? VRS is an inelastic scattering effect Incoming light excites water molecules to vibrations Reemission in the same wavelength (RAYLEIGH scattering) Reemission in other wavelength (RAMAN scattering) FIZ, Berlin (http://vs-c.de)

6. ESA Frascati 31 Oct 2014dinter@iup.physik.uni-bremen.de 6 Vibrational Raman Scattering in liquid water Transspectral processes causes filling in of absorption or FRAUNHOFER-lines More photons are shifted into than out of the lines I - : original ; I + : after filling in process Defining pseudo-absorber like in DOAS-method after BEER- LAMBERT-Law

7. ESA Frascati 31 Oct 2014dinter@iup.physik.uni-bremen.de 7 Vibrational Raman Scattering in liquid water Modeled with SCIATRAN Transspectral processes causes filling in of absorption or FRAUNHOFER-lines More photons are shifted into than out of the lines I - : original ; I + : after filling in process Defining pseudo-absorber like in DOAS-method after BEER- LAMBERT-Law

8. ESA Frascati 31 Oct 2014dinter@iup.physik.uni-bremen.de 8 Vibrational Raman Scattering in liquid water Excitation at 390-444.5nm Reemission at 450-524nm

9. ESA Frascati 31 Oct 2014dinter@iup.physik.uni-bremen.de 9 Model Scenario SCIATRAN (Rozanov et al. 2014)  Clear Rayleigh, Ozone Atmosphere  Reference solar zenith angle 40°  Ocean:  500m homogeneous mixed water body, black albedo  Surface: Cox & Munk (1954) approx. (wind speed 4.1 m/s)  Standard chl-a CASE-I water model (Morel et al. (1991) and Prieur & Sathyendranath (1981)) for absorption  Molecular (Rayleigh) scattering by Buiteveld et al. (1994)  Particle scattering based on bi-modal distribution model of Kopelevich (1983)  Conc. of small and large particles are determined by one parameter model of Haltrin (1999)

10. ESA Frascati 31 Oct 2014dinter@iup.physik.uni-bremen.de 10 VRS Weighting Function from TOA radiance simulations C = 0.1 mg/m^3 C+ΔC = 0.11 mg/m^3

11. ESA Frascati 31 Oct 2014dinter@iup.physik.uni-bremen.de 11 Weighting Function Differential Optical Absorption Spectroscopy (WF-DOAS)

12. ESA Frascati 31 Oct 2014dinter@iup.physik.uni-bremen.de 12 VRS-WF Ocean IOPs without VRS AtmospherePolynom Weighting Function Differential Optical Absorption Spectroscopy (WF-DOAS)

13. ESA Frascati 31 Oct 2014dinter@iup.physik.uni-bremen.de 13 VRS-WF Ocean IOPs without VRS AtmospherePolynom Weighting Function Differential Optical Absorption Spectroscopy (WF-DOAS)

14. ESA Frascati 31 Oct 2014dinter@iup.physik.uni-bremen.de 14 Modeling subsurface radiation to determine light availability (DISI) - Integrated over VRS excitation (390 – 444.5nm) - Reference solar zenith angle 40° - The less chl-a the more light is available in the ocean water

15. ESA Frascati 31 Oct 2014dinter@iup.physik.uni-bremen.de 15 - Integrated over VRS excitation (390 – 444.5nm) - Reference solar zenith angle 40° - The less chl-a the more light is available in the ocean water Modeling subsurface radiation to determine DISI: Change with chl-a conc.

16. ESA Frascati 31 Oct 2014dinter@iup.physik.uni-bremen.de 16 Modeled relationship between DISI and VRS fitfactor + => Fitfactor (strength) of VRS signal has a nearly linear relationship to DISI

17. ESA Frascati 31 Oct 2014dinter@iup.physik.uni-bremen.de 17 Simulating effects of different absorptions and profiles Different specific absorption spectraDifferent profiles (Uitz et al.)

18. ESA Frascati 31 Oct 2014dinter@iup.physik.uni-bremen.de 18 Simulating effects of different absorptions and profiles + => Leads to a maximum error of ~10%

19. ESA Frascati 31 Oct 2014dinter@iup.physik.uni-bremen.de 19 DISI dependence on solar zenith angle

20. ESA Frascati 31 Oct 2014dinter@iup.physik.uni-bremen.de 20 Accounting for solar zenith angle in Look-up Table

21. ESA Frascati 31 Oct 2014dinter@iup.physik.uni-bremen.de 21 [phot/sec/m] SCIAMACHY DISI from VRS WF-DOAS fit (sza corr)

22. ESA Frascati 31 Oct 2014dinter@iup.physik.uni-bremen.de 22 SCIAMACHY VRS WF-DOAS fit

23. ESA Frascati 31 Oct 2014dinter@iup.physik.uni-bremen.de 23 Summary and Outlook  A new method is introduced to determine the light availability from VRS effect  Has the potential to determine PAR directly (without former determination of a, b, and PAR(0+))  Applicable to other hyperspectral sensors like GOME-2, OMI, or upcoming TROPOMI with different overpass times (-> daily cycle)  Publication submitted at OS

24. ESA Frascati 31 Oct 2014dinter@iup.physik.uni-bremen.de 24 Thank You for Attention! End

25. ESA Frascati 31 Oct 2014dinter@iup.physik.uni-bremen.de 25 Appendix Modeling subsurface radiation to determine DISI

26. Comparison